Thousands of Northern Rock customers beseiged the crisis-hit bank again today, many driven by concern that it might not have a future.

At Houndsditch, near London's Liverpool Street station, the queue of customers patiently waiting stretched many metres beyond the branch. Some said that they were keen to withdraw their money while Northern Rock was still solvent.

Mrs Pauline Yates said the sight of long queues outside branches over the weekend had encouraged her to withdraw her own savings.

"You don't want to be the mug who's left without their money when the bank folds," she said.

Anxious savers at some Northern Rock branches had started queuing as early as 3am today.

At 10.30 this morning, a customer at the front of the Houndsditch queue said he had been waiting since 8am. Northern Rock had posted a security guard at the front of the branch, but there was no sign of disorder among the 70 or so customers waiting to gain access.

Over at Moorgate, the queue stretched around two corners, with many customers waiting their turn in a gloomy tunnel. Almost 200 people were waiting by 11am. With Northern Rock only allowing one more customer inside every 15 minutes, it appeared highly unlikely that everyone queueing would get inside today - even though the branches had opened an hour earlier at 8am and are staying open an hour later, to 6pm.

One woman said she was not impressed with Alistair Darling's repeated appearances on television, reassuring the nation that Northern Rock was solvent. She wants Mervyn King to take a larger role.

"It shouldn't be the chancellor, it should be the governor of the Bank of England," she said.

Another customer said he had tried to withdraw his savings at another London branch on Saturday, but had been turned away.

"I got back to my car to find a £50 parking ticket," he fumed.

The continued drop in Nothern Rock's share price had encouraged Rik Saunderson to take out his money.

"That might precipitate the company being bought out, which means my money is safe, but at the same time it means that I don't have control over which bank has my money, the stock market does," he explained.

Romilly Turton criticised them for paying themselves generous bonuses in April, just days after the Financial Services Authority warned the company that the sub-prime mortgage problems in America could damage them.

"Alarm bells should have been ringing once the credit crisis began," said Mr Turton, as he queued outside the Houndsditch branch.

John Bateman, whose financial analyst son had advised him to withdraw his savings, suggested that chief executive Adam Applegarth has been "a bit of a cavalier" by underpinning the group's mortgage business with money borrowed on a short-term basis.

But another customer said the board had acted properly by agreeing a loan facility with the Bank of England.

It was the same story throughout the country today - in Leeds, around 100 people were queuing outside the Northern Rock on Briggate. Some had even brought chairs and flasks to make their wait more comfortable.

Pensioner Chris Robertson, 67, said he had a lot of money at stake but did not want to take a risk.